1. Field of the Invention
This invention relates to an ultrasonic bonding machine for bonding an overlapped interface between a plurality of members to be bonded together with vibration of a vertical ultrasonic wave having a predetermined frequency.
2. Description of the Prior Art
FIG. 14 is a side view of an ultrasonic bonding machine disclosed in Japanese Patent Publication 23349/1979. In FIG. 14, a base 200 includes a hydraulic cylinder 201 like a hydraulic jack constituting a pressure mechanism at the center thereof. On top of a piston rod 202 which projects upward from the top surface of the base 200 of the hydraulic cylinder 201, there is provided a mount 203 for mounting an overlapped interface Wa between members W1 and W2 to be bonded together. A transducer 204 is an so-called electro-acoustic converter or electric vibration converter for converting electric energy into mechanical energy and formed of a piezoelectric element, a magnetostriction element or the like, which generates and outputs vibration of a vertical ultrasonic wave having a predetermined frequency with electric energy received from an unshown ultrasonic wave generator through a cable 205. A bar-shaped resonator 207 is connected mechanically to the output end 206 of this transducer 204 in such a manner that it is coaxial with the transducer 204.
At the maximum vibration amplitude point at the center of the resonator 207, there is provided a bonding working portion 208 which projects outward in a radial direction from the outside surface of the resonator 207. One ends of support members 209 and 210 are connected to the two maximum vibration amplitude points on both sides of the resonator 207, respectively. The other ends of these support members 209 and 210 are connected to the left and right end surfaces of the base 200, respectively. The bottom surface of the bonding working portion 208 and the top surface of the mount 203 are arranged to face each other in a direction perpendicular to the transmission direction of ultrasonic vibration from the transducer 204 to the resonator 207 due to the connection relationship between the resonator 207 and the base 200 by means of the support members 209 and 210.
Therefore, the resonator 207 including the transducer 204 is arranged above the base 200 and parallel to the base 200 by means of the two support members 209 and 210 with a predetermined space formed therebetween. When the piston rod 202 of the hydraulic cylinder 201 stops at the lowermost position, the interface Wa is mounted on the top surface of the mount 203, and the piston rod 202 expands and stops at the uppermost position, the top surface of the interface Wa mounted on the top surface of the mount 203 is pressed against and brought into contact with the bottom surface of the bonding working portion 208 and the bottom surface of the interface Wa is also pressed against and brought into contact with the top surface of the mount 203 during the period from the time when the piston rod 202 moves up from the lowermost position to the time when the piston rod 202 stops at the uppermost position. As the result, the interface Wa is pressure-held between the mount 203 and the bonding working portion 208.
Either after or before the pressure-holding, electric energy is supplied from an unshown ultrasonic wave generator to the transducer 204 to enable the transducer 204 to generate ultrasonic vibration. The ultrasonic vibration generated by the transducer 204 is transmitted to the bonding working portion 208 through the resonator 207 while the interface Wa is pressure-held so as to vibrate the bonding working portion 208 in a direction perpendicular to the direction of pressurization by the hydraulic cylinder 201. After an elapse of time, this vibration causes non-fusion bonding of the overlapped surfaces of the interface Wa, as disclosed in U.S. Pat. No. 2,946,119, for example.
In the above ultrasonic bonding machine of the prior art, since the resonator 207 is attached to the base 200 by means of the support members 209 and 210 formed separately, when the resonator 207 is exchanged with another resonator, it is necessary to disconnect the support member 210 from the resonator 207, remove the support member 210 from the base 200 or move an upper end of the support member 210 on this side or the other side on the paper of FIG. 14, disconnect the resonator 207 from the support member 209, and remove the resonator 207 from the base 200. In this way, the exchange of the resonator is troublesome. Since the interface Wa is pressure-held by lifting the mount 203 by means of the hydraulic cylinder 201, the prior art involves the problem that the interface Wa is held between the bonding working portion 208 and the mount 203 while the interface Wa is horizontally displaced during its upward movement.
One of possible solutions to this problem is that the mount 203 is set still and the resonator 207 is moved vertically while it is arranged horizontally. However, when this resonator 207 is incorporated into a production line, a working space between the resonator 207 and the mount 203 must be widened in a vertical direction due to the relationship between the pre-step and post-step of the bonding step or the relationship between it and the shapes of members W to be bonded together. When a wide working space is formed in the vertical direction, a portion of the machine for housing the pressure mechanism 201 for moving the resonator 207 vertically becomes large in height, thus retrograding from reductions in the size, weight and energy consumption of the entire machine. Therefore, the ultrasonic bonding machine of the prior art is hardly employed.